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Some birds massage each other, according to a new study that found the stress levels of both masseuses and their subjects are lowered after their quality time together.

The study, published in the latest issue of Royal Society Biology Letters, further determined that subordinates seem to enjoy massages the most when they are given by their superiors.

"It may be that subordinates are more likely to be the stressed ones in a group," Andy Radford, author of the study, told Physorg.com. "So if they get a massage from a usually threatening dominant individual, it's particularly relaxing, because it means they're accepted and so feel secure."

Radford, a researcher in the School of Biological Sciences at the Unviversity of Bristol, focused his attention on green woodhoopoes, large tropical birds native to Africa. After receiving massage-like grooming by another bird, they reduce their activity levels and relax in a sort of happy stupor for a noticeable period.

Other birds engage in such behavior too, apparently even with other species. Check this out:

(Looks like the cat is torn between submission and taking a bite out of the parrot's foot.)

Scientists are interested in this kind of behavior for a number of reasons. One is because they wonder why individuals spend time and energy on others when the rewards aren't apparent and immediate. In this case, the individuals being groomed and massaged receive a clear benefit, but what about the masseuses?

In the paper, Radford writes that "they might be trading grooming for food, tolerance, or participation in later intragroup or intergroup conflicts. There is also some evidence that allo-grooming donors experience lower long-term stress levels than recipients, and grooming others might even be self-rewarding."

Other studies suggest these findings could apply to primates as well, so we humans might even take note.